Georgia and other states with a history of overt racial discrimination are required to get federal “preclearance” for any change to their election systems. Wednesday, the U.S. Supreme Court will hear a case that seeks to strike down that provision of the Voting Rights Act. This week, the AJC is looking into the issues at stake in the hearing.

Sunday: Fulton County embodies the struggles of the past

Monday: The new face of voting rights issues

Tuesday: Did the act foster partisan gridlock?

Wednesday: A historic day for a historic law

The Voting Rights Act has done what it was intended to do: bolster the political fortunes of racial and ethnic minorities. But the landmark civil rights bill has also done something that wasn’t planned: feed the sharp partisanship that has tied the nation’s government in knots.

By dramatically expanding the ranks of minority voters and establishing congressional and legislative districts designed to elect minorities, the act has intensified political polarization, many scholars and analysts say. Nowhere is that impact felt more than in the old Confederacy, where Jim Crow laws have yielded to decades of federal oversight at the ballot box.

As the U.S. Supreme Court considers this week whether a key provision of the 1965 law passes constitutional muster, Congress and the White House are embroiled in yet another high-stakes showdown. Across-the-board spending cuts known as sequestration are feared and loathed by both parties. Yet, even under the threat of sequestration, a bipartisan compromise on deficit reduction remains elusive.

So there’s little doubt that the political climate is partisan. But is it more so than it used to be?

Keith Poole, a political science professor at University of Georgia, says yes. Poole came up with a statistical method to analyze every roll call vote taken in Congress.

His conclusion: Congress is now the most polarized it’s been since 1879.

“Republicans have moved steadily out to the right and Democrats to the left,” Poole said. “They are the farthest apart they have been since Reconstruction.”

Richard Pildes, a constitutional law professor at New York University who has studied the issue, says a key reason is the Voting Rights Act.

Signed into law by President Lyndon Johnson in 1965, the law removed barriers such as literacy tests, which kept millions of African Americans throughout the South from registering to vote. As a result, those disenfranchised citizens registered to vote and began casting ballots.

Until that time, the South had been a solid Democratic monopoly, a sometimes uneasy alliance between urban black elected officials and rural, conservative whites.

With more blacks voting, the center of power in the party shifted. White conservatives fled to the Republican Party, creating a genuine two-party system in the South — a system in which Democrat is largely synonymous with black and liberal, and Republican basically means white and conservative.

The Voting Rights Act also prohibited states and local jurisdictions from drawing district lines in a way that divided up concentrations of black voters, making it impossible for them to elect the candidates of their choice. Those provisions were strengthened when Congress amended the act in 1982 and the Supreme Court interpreted the new language four years later.

That 1986 ruling effectively said that anywhere that voting is racially polarized (meaning that whites don’t support minority candidates), states and localities must do all they can to create safe minority districts. The first major application of the court’s decision came with the redistricting of the early 1990s.

In 1994, Republicans racked up a huge net gain of 54 House seats, catapulting Georgia Republican Newt Gingrich into the role of House Speaker. A critical driver in that historic GOP takeover was Republican gains in the South, and those gains derived from newly polarized districts, according to a University of Georgia political science professor who has written extensively on the Voting Rights Act.

“Beginning in the ’90s, legislatures created a lot more minority districts, ‘bleaching’ the surrounding districts,” said Charles Bullock. The big winner, he said, was the GOP, which now controls Southern politics in a way that hearkens back to the old “Dixiecrat” machine. The only Southern states to vote for Obama last year were Virginia, a border state, and Florida, a mega-state heavy with immigrants and Northeastern transplants.

The South is also the focus of the most stringent supervision under the Voting Rights Act. Section 5 — the one the Supreme Court has been asked to strike down — requires jurisdictions with a history of voter suppression to get federal approval before changing any election process.

Georgia, like the nation, has become increasingly split along racial and party lines in recent years. Today the state sends some of the most liberal members to the U.S. House from majority-minority districts, such as John Lewis of Atlanta and Hank Johnson of DeKalb County. The state also sends a handful of the most conservative Republicans, such as Paul Broun of Athens and Tom Graves of Ranger, both tea party favorites. The state’s newest district in northeast Georgia, drawn in the last round of redistricting, is rated as one of the most conservative in the nation.

In 2010, the winners of the state’s congressional races beat their general election opponents by an average of 48 percentage points — 10 points is generally considered a landslide. Only two of 13 races were at all competitive, and three Republicans had no general election opponent.

And in 2008, exit polls showed that Obama won 98 percent of black voters in the state, while 76 percent of white voters selected Republican John McCain. Exit polls weren’t conducted in the state in the 2012 presidential race.

Not everyone agrees that the Voting Rights Act is responsible for political gridlock. As evidence, they point to the U.S. Senate, which has also become more polarized with members elected statewide, immune from the racial and political gerrymandering that shapes many House districts.

They also argue that the law itself is less to blame than how it has been implemented.

“I think in some cases you have seen the Voting Rights Act as an excuse, as a cover, for gerrymandering,” said Emory University political science professor Alan Abramowitz. He believes Republicans have sometimes used the law to “pack” minorities into districts.

But the opposite, “unpacking” them, can be legally and politically dicey.

In 2000, Georgia Democratic leaders sought to slow Republican gains by unpacking minority districts in the state legislature, spreading black, reliably Democratic voters among as many districts as possible. The resulting Supreme Court ruling, Georgia v. Ashcroft, slapped them down. It held that that Democrats, the party of minorities, cannot dilute minority voting strength even in the name of thwarting Republicans, the party of whites.

U.S. Rep. Lynn Westmoreland, a Coweta County Republican who has been involved in GOP redistricting efforts nationwide, voted against re-authorization of the Voting Rights Act when it last came before Congress in 2006. He said one of the problems is that the Department of Justice has not laid out a precise standard for how many minority voters a district must have to meet federal requirements.

“Is it 50 (percent) plus one? Is it 55? Is it 45? What’s the number that it takes to have influence?” Westmoreland asked.

Pildes, the professor who believes the Voting Rights Act has fed hyper-polarization, said that, on balance, the act may still be worth the trade-off. He points to the protections it has offered for minority voters and the uptick in minority officeholders since the law took effect, which he labeled worthy objectives.

“Maybe the benefits are worth it,” he said. “But to argue they haven’t come at a cost would be wrong.”